Motor control unit for table-type electronic calculator with printer

ABSTRACT

The motor operating a printer is on only for as long as necessary to print each keyed-in character, and shuts off for idle periods. The depression of a keyboard key produces a signal which discharges a capacitor, whereby a motor drive transistor is rendered conductive to start the motor. A control circuit is provided which responds to a signal produced for each revolution of the motor and to a clock pulse signal produced in response to a depressing operation of the keyboard to permit the passage of a character pulse synchronized with the rotation of a printer drum to thereby initiate a printing operation. After the printing operation, in the absence of a depressing operation of the keyboard, the charging of the capacitor causes the drive motor to stop, thus enabling an automatic start and stop of the motor in accordance with a depressing operation of the keyboard.

United States Patent [191 Sato et al.

[ Mar. 11,1975

1 MOTOR CONTROL UNIT FOR TABLE-TYPE ELECTRONIC CALCULATOR WITH PRINTER[75] Inventors: Yostbumi Sato; Masaaki Ogura,

both of Tokyo, Japan [30] Foreign Application Priority Data July 17,1972 Japan 47-84230 [52] US. Cl ..197/17, 235/61,197/12 [51] Int. Cl.B4lj 23/08 [58] Field of Search 197/11-17, 197/1; 200/33; 235/61; 101/93C [56] References Cited UNITED STATES PATENTS 2,665,792 1/1954 Stauss197/17 2,802,163 8/1957 Lambert et al. 197/17 X 2,919,781 l/l960 Rix etal. l97/17 3,354,372 11/1967 Beasley 197/17 X 3,700,087 lO/l972 Ahrns eta1. 197/17 3,753,004 8/1973 Dominic 307/121 OTHER PUBLICATIONS Schaefer,lBM Technical Disclosure Bulletin, Vol. 7,

No. 4, Sept., 1964,-pp. 315-316.

Primary Examiner15dgar S. Burr Assistant Examiner-Edward M. CovenAttorney, Agent, or FirmCooper, Dunham, Clark, Griffin & Moran v 57ABSTRACT The motor operating a printer is on only for as long asnecessary to print each keyed-in character, and shuts off for idleperiods. The depression of a keyboard key produces a signal whichdischarges a capacitor, whereby a motor drive transistor is renderedconductive to start the motor. A control circuit is provided,

which responds to a signal produced for each revolution of the motor andto a'clock pulse signal produced in response to a depressing operationof the keyboard to permit the passage of a character pulse synchronizedwith the rotation of a printer drum to thereby initiate a printingoperation. After the printing operation, in the absence of a depressingoperation of the keyboard, the charging of the capacitor causes thedrive motor to stop, thus enabling an automatic start and stop of themotor in accordance with a depressing operation of the keyboard.

4 Claims, 2 Drawing Figures MOTOR CONTROL UNIT FOR TABLE-TYPE ELECTRONICCALCULATOR WITI-I PRINTER BACKGROUND OF THE INVENTION The inventionrelates to a motor control unit for table-type electronic calculatorwith a printer, and more particularly to such a unit in which the startand stop of the printer driving motor is automatically controlled by adepressing operation of the keyboard.

In an apparatus having a motor, for example in a table-type electroniccalculator having a printer, the usual practice of operating the motoris to provide a main switch which is turned on and stays on untilmanually turned off. With such an arrangement, the motor remainsrotating even when the calculator is not in actual use, which causesunnecessary and undesirable noise and a temperature rise within theapparatus.

SUMMARY OF THE INVENTION An object of the invention to overcome theabovedescribed drawbacks and toprovide a motor control unit capable ofreducing noise and temperature rise by activating the motor only for agiven time interval following the operation of a keyboard key.

In the motor control unit according to the invention, the motor isoperated for a given time interval following the operation of a keyboardkey, and thus noise and temperature rise'can be substantially reduced.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF A PREFERREDEMBODIMENT OF INVENTION Referring to FIG. 1, a table-type electroniccalculator with a printer with which the motor control unit of theinvention is associated includes a plurality of keys on a keyboard (notshown), the depression of any of which produces an input pulse trainwhich is applied to an orcircuit OR,. For example, when one of thesymbol keys of a first group on the keyboard is depressed, a clock pulsetrain from a clock pulse generator (not shown) is applied to the inputterminal 11 of the or-circuit OR,, and when one of the symbol keys of asecond group on the keyboard is depressed, a clock pulse train from theclock pulse generator is again applied to the input terminal 12 of theor-circuit OR,. If required, the orcircuit OR, may include a third inputterminal 13 to which a clock pulse train from the'clock pulse generatormay be applied when any one of the numeral keys on the keyboard isdepressed. The output terminal of the or-circuit OR is connected withthe both input terminals of and-circuit AND,, the output terminal ofwhich is connected to the base of an NPN transistor TR, through aresistor R,. The transistor TR, has its collector grounded at GNDthrough a resistor R and also connected to the cathode of a diode D, andhas its emitter connected with a negative d.c. supply V The anode of thediode D is connected with the junction A between a resistor R and acapacitor C, which constitute an integrating circuit connected in seriesbetween the negative d.c. supply and ground. The junction A is connectedwith the input terminal of an inverter INV,. When a numeral key isdepressed, a pulse train as shown in FIG. 2 (a) is applied through theorcircuit OR, and and-circuit AND, to the base of the transistor TR,,which therefore conducts. As a result, the capacitor C isshort-circuited through the diode D and transistor TR,,and the chargethereon is instantaneously discharged to bring the potential at A to alow potential level shown in FIG. 2 (c). This results in a highpotential output from the inverter INV,, which is applied through anor-circuit OR, and an inverter INV, to the base of a PNP transistor TRthereby rendering PNP transistors TR, and TR, conductive to cause a dc.motor M to rotate during the high level signal shown in FIG. 2 (b). Thetransistor TR and TR;, constitute a drive circuit for the dc. motor M.The base of the transistor TR is connected through a resistor R to theoutput terminal of the inverter IN V, and grounded through a resistor RThe emitter and collector of the transistor TR are connected with thebase and collector, respectively, of the transistor TR which has itsemitter grounded and its collector connected to a negative d.c. supply Vthrough the dc. motor M. The dc. motor M represents the drive source fora printer (not shown) contained in the table-type electronic calculatorwith which the motor control unit of the invention is associated. Thedc. motor M is associatedwith a home pulsegenerator G which produces apulse for every revolution of the motor. The pulse train from this pulsegenerator G-is shown as a home pulse train in FIG. 2 (d), which isapplied to a flipflop circuit F,. The application of a clock pulse froma suitable clockpulse generator (not shown) causes the flipflop circuitF, to be set when the home pulse is applied, and causes the flipflopcircuit to be reset when the home pulse is not applied. The output ofthe flipflop circuit F, is applied to a flipflop circuit F together withthe clock pulse from the clock pulse generator. Upon application of'aclock pulse thereto, the flipflop circuit F is set when the flipflopcircuit F, is set, and is reset when the flipflop circuit F, is reset.The output of the flipflop circuit F, is also applied to an inverter INVthe output of which is applied to an or-circuitOR together with theoutput from the flipflop circuit F and the clock pulse from the clockpulse generator. The or-circuit 0R produces a pulse train, shown in FIG.2 (e), which is in synchronism with the home pulse train. The outputsfrom the flipflop circuit F, and inverter INV, are applied to anand-circuit AND the output of which is applied to a flipflop circuit Ftogether with the output from the or-circuit OR;,. The application ofthe output from the or-circuit 0R to the flipflop circuit F results inthis flipflop circuit F, being set when the output from the and-circuitAND is applied thereto, and results in the circuit F being reset whenthe output from the andcircuit AND is not applied thereto.

The transistor TR, is rendered non-conductive when the input signaloccurring as a result of a depressing operation of the keyboard ceases,and hence the capacitor C commences charging to the level of the supplyvoltage through the resistor R As shown in FIG. 2 (c), the voltage onthe capacitor Creturns to its normal level over a preset time intervalafter the operation of the keyboard, and the output of the inverter INV,is applied to the and-circuit AND, during such interval. As

a result, the flipflop circuit F is set in synchronism with a first homepulse as shown in FIG. 2 (f), and its output is applied to a flipflopcircuit F together with the output from the or-circuit OR;,. Theapplication of the output from the or-circuit OR;, to the flipflopcircuit F causes the circuit F to be set when the flipflop circuit F isset and causes the circuit F, to be reset when the flipflop circuit F isreset. Therefore, the flipflop circuit F is set in synchronism with asecond home pulse as shown in FIG. 2 (g), and its output is applied to aflipflop circuit F together with the output from the orcircuit R Theapplication of the output from the orcircuit 0R to the flipflop circuitF causes the circuit F to be set when the flipflop circuit F is set andcauses the circuit F to be reset when the flipflop circuit F is reset.As a consequence, the flipflop circuit F is set in synchronism with athird home pulse as shown in FIG..

2 (h), and its output is applied to the or-circuit CR and and-circuitsAND; and AND To the and-circuit AND is applied a signal as shown in FIG.2 (i), a so-called character pulse train, which is synchronised with thesignal produced in response to the depression of a numeral key or asymbol key. The and-circuit AND produces a pulse train of the type shownin FIG. 2 (j), which pulse train is applied to an arithmetic unit (notshown) within the table-type electronic calculator to initiate theoperation of a printer contained therein. Subsequently, when the dc.motor M is in the state of steady state rotation, the printer isoperated every time a key is depressed to effect a printing operationthereof. The capacitor C is short-circuited by the transistor TR everytime a key on the keyboard is operated, thereby being instantaneouslydischarged to commence recharging. The time period from the shortcircuiting of the capacitor C until its charging is substantiallycomplete depends on the values of the capacitor C and resistor R Whenthe keyboard is operated at a time interval less than such time period,the output from the inverter INV, is at a high level as shown in FIG. 2(b), so that the dc. motor M continues its steady state rotation and thepulse from the and-circuit AND places the table-type electroniccalculator in an operative condition. When the keyboard ceases to beoperated and the charging of the capacitor C is substantially complete,the output from the inverter INV changeS to a low level as shown in FIG.2 (b), whereby the output from theand-circuit AND ceases. Subsequently,when an output pulse is produced from the or-circuit OR;, in synchronismwith the home pulse train, the flipflop circuit F is reset as shown inFIG. 2 (f). When another output pulse is produced by the or-circuit 0Rsubsequent to the resetting of the flipflop circuit F the flipflopcircuit F is reset as shown in FIG. 2 (g). When a further output pulseis produced by the or-circuit 0R subsequent to the resetting of theflipflop circuit F the flipflop circuit F is reset as shown in FIG. 2(h). When the flipflop circuit F is reset, the transistors TR and TR;,are rendered non-conductive to interrupt the drive of the dc. motor M asshown in FIG. 2 (k), and also the output from the and-circuit ANDceases, as shown in FIG. 2 (j), to make the table-type electroniccalculator inoperative. A signal PF which is produced when a suitablepaper feed switch (not shown) is manually operated is applied to theand-circuit AND, and or-circuit 0R This results in producing an outputfrom the andcircuit AND, in the similar manner as when the tabletypeelectronic calculator is operated or when a symbol key is depressed,which pulse is applied to the paper feed mechanism (not shown) of theprinter to feed a record paper. The waveform shown in FIG. 2 (krepresents the waveform of a drive voltage for the motor.

In this manner, with the arrangement according to the invention, themotor which drives the printer is started in response to a signalproduced upon depression of a key on the keyboard, and the motor isstopped upon termination of the operation of the keyboard byautomatically resetting the motor drive circuit with the home pulsetrain, so that the motor driving the printer is driven only for a giventime interval which is necessary for the printing operation. Thispermits noises and temperature rise resulting from the motor operationto be substantially reduced.

While in certain prior art devices the motor is started by the operationofa key and is stopped in response to each step feed of the recordpaper, such an arrangement requires an unalterably intermittentoperation of the motor. By contrast, the invention provides forintegration of the signals produced in response to the operation ofkeys, by an integrating circuit the output of which activates the motor,thus providing either intermittent or continuous operation of the motordepending on how fast the keys are struck, and providing a simple andinexpensive arrangement assuring a long life.

It should be understood that the invention is not limited to table-typeelectronic calculators, but is equally applicable to any apparatushaving a motor. The number of flipflop circuits F to F, can be suitablychosen depending on the performance of the motor.

What is claimed is:

1. A motor control unit for a table-type electronic calculator with aprinter and a keyboard providing character pulse trains in response tothe operation of a keyboard key, said unit comprising: an integratingcircuit including a capacitor which is discharged by a signal producedin response to the operation of a key on the keyboard and means forcharging the capacitor at a defined rate, an electric motor for drivingthe printer, a drive circuit rendered conductive upon discharge of thecapacitor for starting the motor, means for providing a home pulse foreach revolution of the motor and a clock pulse train upon the operationof a keyboard key, a control circuit including means for providing anoutput signal in response to a defined home pulse and a clock pulsetrain and means for allowing the passage of said character pulse trainto the printer during said output signal, said printer including meansresponding to the output signal from the control circuit to start aprinting operation, means for resetting the control circuit upon thecharging of the capacitor in the absence of an operation of the key, andmeans for interrupting the drive circuit to thereby stop the motor inresponse to said resetting of the control circuit.

2. A device including a printer, a keyboard, means for generating a keysignal in response to the operation of each of a plurality of keyboardkeys and for generating a character pulse train corresponding to theoperated key, and a motor for driving the printer,

wherein the improvment is in a motor control unit comprising:

means for starting the motor in response to said key signal generated inresponse to the operation of a keyboard key;

means for generating a train of home pulses synchronized with the motorrevolutions; control means connecting the character pulse generatingmeans and the printer and responsive to said home pulse train forapplying the character pulse train corresponding to the operated key tothe printer in synchronism with a time period starting with a firstselected pulse of said home pulse train and ending with a subsequentsecond selected home pulse; and means for stopping the motor in responseto said subsequent selected home pulse. 3. A device as in claim 2wherein the first selected home pulse is the N-th home pulse after themotor is started and the second selected home pulse is M home pulsesafter the first selected home pulse, where N and M are integers ofselected values.

4. A device as in claim 2 wherein the control means comprise:

means responsive to the key signal to provide an enabling signal of adefined duration; means for counting the home pulses after the start ofthe enabling signal and for selecting the N-th pulse of its count assaid first selected home pulse; and means for counting the home pulsesafter the end of the said enabling signal and for selecting the M-thpulse of its count as said second selected home pulse.

1. A motor control unit for a table-type electronic calculator with aprinter and a keyboard providing character pulse trains in response tothe operation of a keyboard key, said unit comprising: an integratingcircuit including a capacitor which is discharged by a signal producedin response to the operation of a key on the keyboard and means forcharging the capacitor at a defined rate, an electric motor for drivingthe printer, a drive circuit rendered conductive upon discharge of thecapacitor for starting the motor, means for providing a home pulse foreach revolution of the motor and a clock pulse train upon the operationof a keyboard key, a control circuit including means for providing anoutput signal in response to a defined home pulse and a clock pulsetrain and means for allowing the passage of said character pulse trainto the printer during said output signal, said printer including meansresponding to the output signal from the control circuit to start aprinting operation, means for resetting the control circuit upon thecharging of the capacitor in the absence of an operation of the key, andmeans for Interrupting the drive circuit to thereby stop the motor inresponse to said resetting of the control circuit.
 1. A motor controlunit for a table-type electronic calculator with a printer and akeyboard providing character pulse trains in response to the operationof a keyboard key, said unit comprising: an integrating circuitincluding a capacitor which is discharged by a signal produced inresponse to the operation of a key on the keyboard and means forcharging the capacitor at a defined rate, an electric motor for drivingthe printer, a drive circuit rendered conductive upon discharge of thecapacitor for starting the motor, means for providing a home pulse foreach revolution of the motor and a clock pulse train upon the operationof a keyboard key, a control circuit including means for providing anoutput signal in response to a defined home pulse and a clock pulsetrain and means for allowing the passage of said character pulse trainto the printer during said output signal, said printer including meansresponding to the output signal from the control circuit to start aprinting operation, means for resetting the control circuit upon thecharging of the capacitor in the absence of an operation of the key, andmeans for Interrupting the drive circuit to thereby stop the motor inresponse to said resetting of the control circuit.
 2. A device includinga printer, a keyboard, means for generating a key signal in response tothe operation of each of a plurality of keyboard keys and for generatinga character pulse train corresponding to the operated key, and a motorfor driving the printer, wherein the improvment is in a motor controlunit comprising: means for starting the motor in response to said keysignal generated in response to the operation of a keyboard key; meansfor generating a train of home pulses synchronized with the motorrevolutions; control means connecting the character pulse generatingmeans and the printer and responsive to said home pulse train forapplying the character pulse train corresponding to the operated key tothe printer in synchronism with a time period starting with a firstselected pulse of said home pulse train and ending with a subsequentsecond selected home pulse; and means for stopping the motor in responseto said subsequent selected home pulse.
 3. A device as in claim 2wherein the first selected home pulse is the N-th home pulse after themotor is started and the second selected home pulse is M home pulsesafter the first selected home pulse, where N and M are integers ofselected values.